.app
{
    position: fixed;
    left: 0;
    right: 0;
    top: 0;
    bottom: 0;
    background: #eee;
    font-size: 0.24rem;
    text-align: center;
}
.arrow
{
    width: 0.37rem;
    height: 0.24rem;
    background-image: url(../images/arrow.png);
    background-size: 100%;
    background-position: center;
    background-repeat: no-repeat;
    position: fixed;
    left: 50%;
    bottom: 0.4rem;
    margin-left: -0.18rem;
}
.anim
{
    transition:all 1s;
    -webkit-transition:all 1s;
}